Homework Help

Better Students Ask More Questions.

# What is the measure of the largest angle of triangle ABC if BC=9 , AC=10 and AB=13 ?

Student

eNotes Newbie

• Up
• 0
• Down

What is the measure of the largest angle of triangle ABC if BC=9 , AC=10 and AB=13 ?

Posted by guteskind on May 7, 2011 at 8:19 PM via web and tagged with geometry2, math

College Teacher

Valedictorian

• Up
• 0
• Down

Since the lengths of the 3 sides are given, we'll use the law of cosines to determine the measure of the largest angle.

The largest angle is the opposite angle to the largest length of triangle. Since the length of AB is the largest, then the measure of the angle C has to be determined.

cos C = (BC^2 + AC^2 - AB^2)/2BC*AC

We'll replace the sides by its lengths:

cos C = (81 + 100 - 169)/180

cos C = 12/180

cos C = 1/15

cos C = 0.067

C = 86.2 degrees

The measure of the largest angle of triangle ABC is: C = 86.2 degrees.

Posted by giorgiana1976 on May 7, 2011 at 8:26 PM (Answer #1)

## Related Questions

See all »

Join to answer this question

Join a community of thousands of dedicated teachers and students.